I think it is fine since you've already started to communicate well with him. I would have been totally embarrassed to have seen such things at his age, and unfortunately nasty things come up with harmless searches. (I remember this from doing research in college, even with college filters on.)
If he really enjoys wrestling and is taking it seriously, I think it is good that you are as involved as you are now since he may pursue it in school. I'm more of a rough-housing mom myself and hope that good communication with my boys will let us keep up with stuff like that for a long time. Poor kid. :(